The present invention relates generally to hybrid electric vehicles, and more particularly air conditioning for belt-alternator-starter hybrid electric vehicles.
Some types of hybrid vehicles do not have the capability to provide air conditioning comfort when the vehicle engine is off. To improve the overall fuel economy of the vehicles, however, it is generally preferable to have the engine off as often as possible. Nonetheless, not having continuous air conditioning capability may be unsatisfactory to vehicle occupants as compared to conventional vehicles where the engine runs all of the time, allowing for air conditioning whenever desired.
In order to alleviate this concern, some have proposed systems for hybrid vehicles that provide air conditioning even when the engine is off. For example, some hybrid vehicles include refrigerant compressors that have their own electric motor to drive them. Then, the compressor is driven independently of the engine. Others take this one step further by not only having a separate motor to drive the refrigerant compressor, but also allowing for dual drive where the compressor is driven directly off of the accessory drive belt. However, both of these solutions adds to the weight and cost of the vehicle due to the addition of the extra compressor motor as well as the electronics and cables to operate the motor. Still others have attempted to alleviate this concern by providing thermal storage systems that allow for air conditioning comfort during engine off vehicle operation. But these thermal storage systems still add significant cost and require additional packaging space for the air conditioning system, and some only provide the air conditioning comfort for limited amounts of time before the engine must be restarted.